Dashlight staying on all night

[bigup]

Hi all

i have a Focus 2010 1.6tdci Zetec Estate. Been fine all year and last week had a flat battery. 

I charge it up over night. Seems fine then day later flat battery. 

Checked alternator with a volt meter and it’s charging the battery fine.

then yesterday  I noticed the dash light was on, just the mileage screen, the car hadn’t been used for a whole day/night.

Onto Google and forums,  reading it maybe the ignition switch? But mainly on keyless entry? My car doesn’t have keyless entry. 

Ive reset the IC 10amp fuse under the glove box, tried leaving car without steering lock on to no avail.

all doors close properly and the interior light does go off on each door close. So it seems something else is keeping the ECU awake.

the car does have factory fitted sat nav/Bluetooth so my next step is to unplug this and test again.

the only other thing I can think of is the previous owner installed led rear number plate lights, one of them sometimes needs a tap or two to come on but generally been fine, it passed mot last month, il go grab some standard bulbs today .

anyone got any other ideas ?

Thanks in advance. 

[bigup]

Ok a development.

removed the stereo and unplugged all the cables. Locked the car and low and behold 10 mins later the dash lights are off.. 

One other thing, we have an estate and I have one of them boot mats (more of a durable cloth) and noticed some of it was getting stuck in the lock mechanism. Boot was still closing and locking and also rear interior light was going off as Normal so not sure if this was the issue. 

going to plug the head unit back in later and retest

the wife did say that since the battery went flat and was charged the stereo has not been working. So this could well be the issue. 

Will update in due course. 

[Tdci-Peter]

10 hours ago, bigup said:

removed the stereo and unplugged all the cables. Locked the car and low and behold 10 mins later the dash lights are off..

That is the most common cause of the IC dash light staying on. Many modern radios connect to the car CAN BUS. Activity on this bus keeps the IC active, and probably more important for battery drain, it may keep the ECU active.

Faulty stereos (or their wiring) frequently keep the bus active when they are supposed to be powered down. They have a permanent connection to the car battery, and just use the aux line from the ignition switch as a signal to turn on or off. So internal faults can easily keep parts of the circuits in them active, or feed spurious signals onto the CAN bus.